Influence of the ionosphere, modified by powerful oblique radiowaves, on HF radio wave propagation

Variations of HF probe radio wave parameters caused by the influence on the ionosphere of oblique powerful HF radiowaves are analysed. The analysis is made on the data obtained from the original experiments carried out on single-hop paths in the middle and subauroral latitudes. Powerful and probe waves with some difference in frequency were chosen near MUF and were transmitted in the same direction. The polar diagrams of both transmitting systems overlapped in both the horizontal and vertical planes. The results obtained indicate that the ionospheric plasma parameters can be varied by powerful oblique HF radiowaves under certain geophysical conditions.     

Response of mesospheric ozone to the heating of the lower ionosphere by high-power HF radio emission

We detected a decrease in the intensity of microwave radiation at the atmospheric ozone line at a frequency of 110836.04 MHz during ionospheric modification by high-power HF radiowaves radiated by the Sura Ionospheric Heating Facility. The obtained experimental data allowed us to hypothesize that this effect was caused by the fact that mesospheric ozone was affected by internal gravity waves generated in the E region of the ionosphere during its high-power HF radiowave heating.     

Results of Russian experiments dealing with the impact of powerful HF radiowaves on the high-latitude ionosphere using the EISCAT facilities

We present the results of complex experiments dealing with the impact of powerful HF radiowaves on the high-latitude ionosphere using the European Incoherent Scatter Scientific Association (EISCAT) facilities. During the ionospheric F-region heating by powerful extraordinary (X-mode) polarized HF radiowaves under the conditions of heating near the critical f _H frequency f _H ≈ f _x F2 of the extraordinary wave of the F2-layer, we were first to detect the excitation of intense artificial small-scale ionospheric irregularities (ASIs), accompanied by electron temperature increases by approximately 50%. The results of coordinated satellite and ground-based observations of the powerful HF radiowave impact on the high-latitude ionosphere are considered. During ionospheric F-region heating by powerful HF radiowaves of ordinary polarization (O-mode) during evening hours, the phenomenon of ion outflow accompanied by electron temperature increases and thermal plasma expansion was revealed. Concurrent DMSP-F15 satellite measurements at a height of about 850 km indicate an O⁺ ion density increase. The CHAMP satellite observations identified ULF emissions at the modulation frequency (3 Hz) of the powerful HF radiowave, generated during modulated emissions of the powerful HF radiowave of O-polarization and accompanied by a substantial increase in the electron temperature and ASI generation.     

Ground-based observations and simulation of ionospheric VLF source in experiments on modification of the polar ionosphere

The phase velocities of TE and TEM waves at frequencies of 1017 and 3017 Hz, as well as the effect of precipitations during auroras on the velocities, are estimated in the Earth–ionosphere waveguide on the basis of observations of electromagnetic fields of an ionospheric source in experiments on modification of the lower ionosphere by a modulated high-power short-wave signals performed by the Arctic and Antarctic Research Institute (AARI) at the EISCAT/Heating test bench in October 2016. Probable electron density profiles in the plane-stratified ionosphere are retrieved from the numerical solution of a wave equation, which are used for the calculation of the phase velocities close to measured ones.     

The effect of artificial modification in the E region on HF ray propagation

During RF heating at 4.04 MHz an increase of 5 dB in the signal strength of a 4.2 MHz probe wave has been observed. This is attributed to a heater induced increase in electron density in the E region leading to the opening up of a low angle propagation path from probe transmitter to receiver. The geometry of the experiment is consistent with an electron density increase distributed in a torus in the E region centred above the heater site.     

Model prediction of the most effective frequency for the large-scale modification of the midlatitude ionospheric <Emphasis Type="Italic">F</Emphasis><Subscript>2</Subscript> layer by powerful HF radiowaves

The response of the midlatitude F ₂ layer to the effect of powerful HF radiowaves is studied using the numerical model of the ionosphere. The large-scale modification of the F ₂ layer over the Sura heating facility near Nizhni Novgorod is considered for autumnal conditions. The calculations are performed for various cases when the heating wave has different frequencies under the daytime and nighttime conditions. The calculation results show that large-scale changes in the electron temperature and density in the F ₂ layer caused by the artificial heating should substantially depend on the heating radiowave frequency. It is found that there should exist such, most effective, heating wave frequency at which a decrease in the electron density at the F ₂ layer maximum height over the heating facility should be maximal.     

大功率高频电波加热电离层的非线性物理过程

地基大功率电波加热电离层是通过地基大功率短波发射机向电离层发射无线电波,通过波-粒和波-波的相互作用将无线电波的能量注入电离层.通过这种有目的可操控的方式改变电离层电子密度和温度的分布,可以深入研究电离层中等离子体能量和物质的非线性演化过程,特别是电离层电子的非平衡态分布和加速问题.本文通过对电离层加热中几个比较重要物理过程的评述,对过去20年来我国研究学者在这一研究方向上取得的重要进展进行了介绍.

     

Wave diagnostics of the outer high-latitude ionosphere under application of numerical simulation of ionospheric filtration to simultaneous,conjugate, ground-based and satellite measurements of Pc1 signals

Summary Based on the French conjugate experiment of satellite and ground-based measurements of ULF signals on GEOS-1 and at Husafell, changes of the ionospheric filter in the course of a series of measurements of intensive Pc1 micropulsations (ICW) on 1. 8. 1977 were wave diagnosticated. Changes of the vertical profile of electron concentration in the outer high-latitude ionosphere were simulated numerically by solving approximately the inverse problem using the matrix method of numerical modelling of ionospheric filtration in Pc1 frequencies. It was found that the intensive ICW packets could have propagated through the corridor of the high-latitude ionospheric plasma through. Quantitative estimates of ionospheric changes, however, are usually upset by the effects of other factors in the course of the wave's propagation through the outer magnetosphere.     

Determining the ionospheric irregularity velocity vector based on doppler measurements in the artificially modified <Emphasis Type="Italic">F</Emphasis><Subscript>2</Subscript> region of the polar ionosphere

The method for estimating the behavior of the ionospheric irregularity motion vector in the artificially disturbed HF ionospheric region has been proposed, and this behavior has been analyzed based on the simultaneous Doppler observations performed on several paths using the method of bi-static backscatter of diagnostic HF signals by small-scale artificial ionospheric irregularities. The Doppler measurements were performed during the modification of the auroral ionosphere by powerful HF radiowaves emitted by the EISCAT heating facility (Tromsø, Norway). It has been obtained that the dynamics of the ionospheric irregularity directions in the F region, calculated based on the Doppler measurements of the total vector of the ionospheric irregularity velocity above the Tromsø EISCAT radar at a frequency of 931 MHz, is in satisfactory agreement with such calculations performed using the three-position method.     

The action of chlorine on the ozone layer as given by a zonally averaged two-dimensional model

In order to study the behavior of stratospheric minor constituents related to aeronomic processes and atmospheric transport in the meridional plane, a numerical two-dimensional model is established.This model is applied to the study of chlorine compounds in the stratosphere. A special attention is devoted to the effect in the ozonosphere of an increase of CIX due to anthropogenic activities.